In this method, a brake device of an elevator system is actuated, which brake device is known in principle. The brake device comprises, for example, an electromagnetically disengageable spring-actuated brake and an electronically actuatable electromagnet for disengaging the spring-actuated brake. The braking action is achieved by means of the spring force of at least one spring. On account of the spring force, a pressure element of the spring-actuated brake, which pressure element has a brake lining, rests against a counter surface, for example on a brake disc of the elevator drive, at least when the electromagnets are de-energized. The pressure element can be a pressure plate that can be pressed against the brake disc, or it can be a pressure shoe or brake shoe that can be pressed against a brake drum, for example. By actuating the electromagnet, the braking action can be canceled by the pressure element being lifted from the counter surface, against the action of spring force, by means of the electromagnet.
A brake device of this type, or a comparable brake device, of an elevator system is intended to hold an elevator car of the elevator system in a holding position. An elevator system comprising a plurality of elevator cars comprises an individual brake device for each elevator car. In the interests of improved readability, but without dispensing with further general validity, the following description will proceed using the example of an elevator system having precisely one elevator car which is movable in precisely one elevator shaft. Said elevator system should always be understood to mean an elevator system having a plurality of elevator cars in one shaft or even in a plurality of shafts.
In addition to holding the elevator car in a holding position, a brake device is necessary and designed in order to be able to safely brake the elevator car at any time during operation, that is to say even in the event of a fault situation. Possible fault situations are, for example, unexpected opening of a car door, an excessive travel velocity, loss of holding position, and so on.
When the brake device is activated, the activation often takes place in a manner that results in a maximum braking action. This leads to an intense deceleration that is unpleasant for the passengers in the elevator car. In order to prevent this, systems are known which control, in a closed-loop or open-loop manner, a particular effective braking torque.
JP 2004/131207 A discloses a brake device in which a plurality of electromagnets are actuated in each case by means of a pulse-width modulated actuation signal.
GB 2 153 465 A discloses load-dependent and travel-direction-dependent control of a brake device. EP 1 870 369 A contains explanations for determining mass parameters of an elevator system.